Flies Get Drunk to Kill Off Parasites

Fruit flies can apparently out-drink Frank the Tank and not get sick from alcohol poisoning. Now researchers have found this fraternity-party ability may save flies from a gory death.

The results showed that drunk fruit-fly larvae turned the tables by killing wasp parasites in their bloodstream, essentially causing the parasite's organs to drain from its anus, the researchers found.

Fruit fly larvae feed on the yeast and other fungi from rotting, or fermenting, fruit; during their snacking, the flies are bound to ingest the boozy byproducts of the fungi's fermentation — they are even able to use it as a food source and thrive on food with up to 4 percent alcohol.

Higher alcohol levels can be toxic to the fruit flies, study researcher Todd Schlenke, an assistant professor at Emory University, told LiveScience. "If the alcohol level gets too high, they can't break it down fast enough." The flies in the study only reached about 0.02 percent blood alcohol levels, they would have to drink four times that to reach the blood alcohol level considered illegal for driving.

Read on:  http://www.livescience.com/18513-fruit-flies-alcohol-parasites.html

Parasitism: wasp uses ladybird as “zombie bodyguard”

The parasitic wasp Dinocampus coccinellae is no fool! It controls a ladybird, lays an egg in its abdomen and turns it into the bodyguard of its cocoon. This surprising host-parasite manipulation has been observed and analyzed by researchers from the Laboratoire Maladies Infectieuses et Vecteurs: Ecologie, Génétique, Evolution et Contrôle (CNRS/IRD/Université Montpellier 1) and the Université de Montréal. Although this strategy enables the wasps to protect their larvae from predation, it has a cost: the wasps pay for it in terms of fertility. The researchers have also demonstrated the reversible character of this manipulation: once the larvae have hatched, some ladybirds can recover normal behavior. This work is published on-line on the website of Biology Letters.


Dinocampus coccinellae is a common parasitic wasp of the spotted lady beetle Coleomegilla maculata. Females deposit a single egg in the abdomen of their host, the ladybird, and during larval development (around twenty days) the parasite feeds on the host’s tissues. Then, the wasp larva breaks out through the ladybird’s abdomen, without killing it, and begins spinning a cocoon between the ladybird's legs. The ladybird, partially paralyzed, is forced to stand guard over the cocoon!

The novel manipulation strategy is intriguing in several ways: whereas the immense majority of parasitic wasps kill their host while they grow, the ladybird parasited by D. coccinellae remains alive. In addition, the behavioral manipulation occurs once the larva has left its host.

The mechanisms of this manipulation have been closely scrutinized by Frédéric Thomas’ team at the Laboratoire Maladies Infectieuses et Vecteurs: Ecologie, Génétique, Evolution et Contrôle (CNRS/IRD/Universités Montpellier 1 et 2), in collaboration with researchers from the Université de Montréal. The researchers believe that the ladybird’s atypical behavior results from a manipulation orchestrated by the wasp in order to be protected from predation up to the end of its larval development, in other words up to the emergence of the adult wasp. The scientists have shown in the laboratory that the cocoons of wasps guarded by a ladybird are much less vulnerable to predation than cocoons left on their own, or cocoons guarded by a ladybird killed for experimental purposes. Secretions left by the larva when it breaks out could force the ladybird to protect the cocoon once the larva has come out.

The wasp larva grows by using the resources of its host. However, these resources must remain sufficient for the ladybird, since it cannot feed itself while guarding the cocoon.

This work also enabled the researchers to validate a theoretical model, according to which parasites cannot maximize both their effort of reproduction and manipulation.

The researchers have demonstrated a negative correlation between the length of the ladybird's guarding period and the fecundity of the wasp. Everything happens as if the wasp larva had to “choose” between using the resources of the ladybird to produce eggs (which will be available at the adult age) or making them last while sparing the ladybird and keeping it alive.

Finally, the researchers were surprised to observe that around 25% of the manipulated ladybirds recovered normal behavior after the emergence of the adult wasp, a very rare case of reversible manipulation.


http://rsbl.royalsocietypublishing.org/content/firstcite
http://www.alphagalileo.org/ViewItem.aspx?ItemId=108521&CultureCode=en

The beasties we need near us, for our own sake

Courtney Humphries, contributor

In The Wild Life of Our Bodies, biologist Rob Dunn argues that our modern separation from other species causes more harm than good

THERE has been no shortage of nostalgia for the "good old days" of human prehistory, when our hunter-gatherer ancestors lived in ecological harmony with nature, roaming savannahs instead of cramped in office chairs. In The Wild Life of Our Bodies, Rob Dunn shares the view of modern human life as a paradise lost, but the loss he laments is not merely of a vague sense of being one with nature. What we have sacrificed, he argues, is a physical connection with the species that shaped our bodies - from our physique to the immune system.

As humans became urban and industrial, we also separated ourselves from other species. Pets aside, we have laboured to rid our houses and cities of creatures - not just visible predators and pests but also the microbes on our countertops and hands. Some of these steps were sensible acts of self-preservation, but others were driven by an ideology of humans as separate from nature. Dunn, a biologist at North Carolina State University as well as a science journalist, catalogues the dangers of that ideology.

To illustrate how species influence one another's evolution, he points to the pronghorn, a small antelope-like mammal in North America that runs inexplicably fast. The pronghorn's speed, Dunn says, only makes sense if you consider the large predators that once hunted it. The "pronghorn principle" also applies to the human body. We too are "haunted by ghosts" of parasites, pathogens and predators that shaped our evolution.
Dunn makes the case that the influence of these ghosts can be seen in our immune systems. He highlights early evidence suggesting that chronic inflammatory diseases of modern society, such as Crohn's disease, diabetes and asthma, could be alleviated by repopulating our bodies with the parasites we evolved with. Our bodies rely so much on gut bacteria that we even give them a safe house in the form of the appendix, Dunn points out, yet our love for antibiotics could be undermining this important relationship.

Dunn also highlights research that shows how we are shaped by the species we have eaten - and that once ate us. Our brains are still wired to avoid predators we no longer encounter: our adrenal system responds to modern daily stresses as if they were mortal threats, for example, and one theory holds that our acute vision may have evolved specifically to avoid venomous snakes. Meanwhile, as we domesticated plants and animals in our quest for survival, we too became domesticated, evolving the ability to drink cows' milk and break down the starch in grains more efficiently.

Dunn makes the case for these connections through detours and anecdotes, with lively stories of patients and scientists, and research spanning archaeology, field biology, medicine, ecology and microbiology. The elaborate fungus farms of leafcutter ant colonies, for instance, become a metaphor for understanding how we humans cultivate bacteria with our immune systems. By drawing connections between work that seems unrelated, Dunn repeatedly drives home his key point: we ignore the lessons of ecology at our peril. By trying to separate ourselves from nature, we have tricked ourselves into believing we are self-sufficient.

Looking for a better way forward, Dunn is practical. Rather than issue a blanket call for "more nature", he advocates applying the lessons of studying our own ecology. Instead of surrounding ourselves only with the plants and animals we find most appealing, we also need to be aware of creatures that help keep our instincts sharp, and species like worms and bacteria that keep our immune systems in check.

Dunn doesn't go so far as to suggest letting predators loose in Central Park, but he does argue for more diversity in the species we interact with and eat. As he writes, "What is missing from our lives is not nature, but a kind of nature that most benefits us".

http://www.newscientist.com/blogs/culturelab/2011/06/the-beasties-we-need-near-us-for-our-own-sake.html